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The flexibility and scale of networks achievable by modern cloud computer architectures, particularly Kubernetes (K8s)-based applications, are rivaled only by the resulting complexity required to operate at scale in a responsive manner. This leaves applications vulnerable toEconomic Denial of Sustainability(EDoS) attacks, designed to force service withdrawal via draining the target of the financial means to support the application. With the public cloud market projected to reach three quarters of a trillion dollars USD by the end of 2025, this is a major consideration. In this paper, we develop a theoretical model to reason about EDoS attacks on K8s. We determine scaling thresholds based on Markov Decision Processes (MDPs), incorporating costs of operating K8s replicas, Service Level Agreement violations, and minimum service charges imposed by billing structures. We build on top of the MDP model a Stackelberg game, determining the circumstances under which an adversary injects traffic. The optimal policy returned by the MDP is generally of hysteresis-type, but not always. Specifically, through numerical evaluations we show examples where charges on an hourly resolution eliminate incentives for scaling down resources. Furthermore, through the use of experiments on a realistic K8s cluster, we show that, depending on the billing model employed and the customer workload characteristics, an EDoS attack can result in a 4× increase in traffic intensity resulting in a 3.6× decrease in efficiency. Interestingly, increasing the intensity of an attack may render it less efficient per unit of attack power. Finally, we demonstrate a proof-of-concept for a countermeasure involving custom scaling metrics where autoscaling decisions are randomized. We demonstrate that per-minute utilization charges are reduced compared to standard scaling, with negligible drops in requests. 

Timeseries monitoring systems such as Prometheus play a crucial role in gaining observability of the underlying system infrastructure. These systems collect timeseries metrics from various system components and perform monitoring queries over periodic window-based aggregations (i.e., rule queries). However, despite wide adoption, the operational costs and query latency of rule queries remain high. In this paper, we identify major bottlenecks associated with repeated data scans and query computations concerning window overlaps in rule queries, and present PromSketch, an approximation-first query framework as intermediate caches for monitoring systems. It enables low operational costs and query latency, by combining approximate window-based query frameworks and sketch-based precomputation. PromSketch is implemented as a standalone module that can be integrated into Prometheus and VictoriaMetrics, covering 70% of Prometheus' aggregation over time queries. Our evaluation shows that PromSketch achieves up to a two-order-of-magnitude reduction in query latency over Prometheus and VictoriaMetrics, while lowering operational dollar costs of query processing by three orders of magnitude compared to Prometheus and by at least 4× compared to VictoriaMetrics with at most 5% average errors across statistics.